The vitamin D derivative represented by Formula (1):
(chemical name: [{(5Z,7E)-(1S,3R,20S)-1,3-dihydroxy-9,10-secopregna-5,7,10(19),16-tetraen-20-yl}oxy]-N-(2,2,3,3,3-pentafluoropropyl)acetamide, or [{1α,3β-dihydroxy-9,10-secopregna-5,7,10(19),16-tetraen-20(S)-yl}oxy]-N-(2,2,3,3,3-pentafluoropropyl)acetamide, or N-(2,2,3,3,3-pentafluoropropyl)-[{(1S,3R,5Z,7E,20S)-1,3-dihydroxy-9,10-secopregna-5,7,10(19),16-tetraen-20-yl}oxy]acetamide) exhibits useful human keratinocyte growth inhibition activity while its harmful calcium level-raising activity is lower than the conventional vitamin D derivatives, so that it is useful as a therapeutic agent for skin disorders such as psoriasis. It is known that this compound is produced by reacting [{1α,3β-bis(tert-butyldimethylsilyloxy)-9,10-secopregna-5,7,10(19),16-tetraen-20(S)-yl}oxy]acetic acid obtained through a photoreaction using 1α,3β-dihydroxy-5-androsten-17-one as a starting material, with 2,2,3,3,3-pentafluoropropylamine (see WO 2001/096293 (Patent Literature 1)).
As examples of the synthetic method of a vitamin D derivative using a palladium catalyst, the methods described in J. Am. Chem. Soc., 1992, 114, 1924-1925 (Non-patent Literature 1), J. Am. Chem. Soc., 1992, 114, 9836-9845 (Non-patent Literature 2) and JP 9-12502 A (Patent Literature 2) are known.
As an example of deprotection of a vitamin D derivative using methanesulfonic acid, JP 8-225480 A (Patent Literature 3) is known.    Patent Literature 1: WO 2001/096293    Patent Literature 2: JP 9-12502 A    Patent Literature 3: JP 8-225480 A    Non-patent Literature 1: J. Am. Chem. Soc., 1992, 114, 1924-1925    Non-patent Literature 2: J. Am. Chem. Soc., 1992, 114, 9836-9845